The instant invention pertains to a method for preventing the loss of brightness and for enhancing resistance to yellowing in pulp or paper which still contains lignin by the addition of nitroxides, hydroxylamines or their salts and other coadditives. The instant invention also pertains to novel compounds which are selected derivatives of 1-oxyl-2,2,6,6-tetramethylpiperidin-4-ol or which are their hydroxylamine salts.
High-yield and ultra-high yield wood pulps undergo rapid light-induced discoloration, particularly when they are exposed to near ultraviolet light (wave lengths 300-400 nm) in indoor fluorescent light and daylight. This characteristic restricts their use to short-life, low-value paper products. High-yield and ultra-high yield wood pulps can be bleached to a high level of whiteness. If this whiteness could be stabilized against discoloration, these bleached high-yield pulps could displace significant amounts of more expensive fully-bleached, low-yield chemical pulps.
This discoloration is ascribed to the substantial lignin content of high-yield pulps totaling about 20-45% by mass. Phenoxy radicals are the key intermediates in the reaction mechanism. Several light-induced reactions have been proposed to account for their formation such as abstraction of a hydrogen atom from phenolic groups, cleavage of the aryl ether bond of phenacyl aryl ether groups, or breakdown of ketyl radicals formed from saturated aryl-glycerol xcex2-aryl ether structures in lignin. The phenoxy radicals are oxidized by other oxygen-centered radicals (alkoxy, peroxy, hydroxy and perhydroxy) to form yellow chromophores. (C. Heitner in xe2x80x9cPhotochemistry of Lignocellulosic Materialsxe2x80x9d, C. Heitner, J. C. Scaiano, eds,: ACS Sym. Ser. 531, 1-25 (1993).)
I. E. Arakin et al., Khymiya drevesiny (Chemistry of Wood), 1982, No.2,114 and A. D. Sergeev et al., ibid, 1984, No. 5, 20 disclosed that the use of iminoxyl radicals such as TEMPO (1-oxyl-2,2,6,6-tetramethylpiperidine) is useful in the delignification of wood using the one-stage oxygen-soda (alkaline) process, but made no mention or suggestion of any activity provided by TEMPO on preventing light-induced discoloration of paper or pulp made from such treated wood.
EP 717,143 and WO 97/36041 describe a multicomponent system for changing, reducing or bleaching lignin and lignin-containing materials which comprise a oxidation catalyst, and a N-hydroxyl mediator compound such as a N-hydroxyphthalimide or a dialkylhydroxylamine. These references are aimed at the delignification of wood. There is no mention or suggestion of any activity provided by the N-hydroxyl compounds in preventing the light-induced discoloration of paper or pulp made from such treated wood.
V. I. Khodyrev et al., Vysokomol soyed, A29, No. 3, 616 (1987) [Polymer Sci. U.S.S.R., 29, No. 3, 688 (1987)] show that the photoinitiated oxidation by oxygen causes weathering of cellulosic textile materials such as flax or cotton. The UV absorbers offer no protection, and are actually detrimental. The authors noted that the stable nitroxyl radical 1-oxyl-2,2,6,6-tetra-methyl-4-hydroxypiperidine interacts with alkyl radicals in the cellulose to afford its salubrious stabilizing activity. There is no suggestion by the authors that this stabilizing activity could be applied successfully in lignin-containing pulp and/or paper made therefrom.
M-K. Syker et al., J. Assn. Paper Pulp Tech, 29, 135 (1990) show that selected metal salts such as magnesium sulfate and lower alkanoic acids inhibit color reversion in bleached pulp.
P. Fornier de Violet et al., Cellulose Chem. Tech., 24, 225 (1990) show that the use of UV absorbers and hydrogen donor agents such as thiols, ascorbic acid, etc. help prevent the photoinduced discoloration of hydrogen peroxide bleached wood pulp, but that chain breakers such as hindered phenols and hindered amines (having  greater than Nxe2x80x94H or  greater than Nxe2x80x94CH2xe2x80x94 moieties) had no or even a detrimental effect on preventing photoinduced discoloration.
R. Agnemo et al., Holzforschung (1991), 45 (Suppl), 101, confirmed that free hydroxyl radicals plus lignin lead to undesirable photoyellowing in pulp and paper.
S. Omori et al., J. Assn. Paper Pulp Tech, 48, 1388 (1993) describes the effect of antioxidants and UV absorbers on light reversion and concludes that the combination of an antioxidant and UV absorber prevents color reversion and has a synergistic effect in that activity.
M. Paulsson et al., Nordic Pulp Pap. Res. J., (1995), 10 (1), 62-67, show that efficient photostabilization of unbleached paper or hydrogen peroxide bleached TMP pulp can be achieved by acetylation.
There have been a number of different approaches proposed to inhibiting the yellowing of mechanical pulps. These include: radical scavengers and antioxidants; UV screens; elimination of chromophores after their formation; chemical modification of lignin by alkylation or acetylation; polymeric inhibitors; and two types of coadditives used in combination. Z-H. Wu et al., Holzforschung, 48, (1994), 400 discuss the use of radical scavengers like phenyl-N-tert-butylnitrone to reduce the formation of chromophores during mechanical pulping and give a more light-stable pulp.
C. Heitner, xe2x80x9cChemistry of Brightness Reversion and It Control, Chapter 5xe2x80x9d, in Pulp Bleaching-Principles and Practice, C. W. Dence, D. W. Reeve, eds., TAPPI Press, Atlanta, 1996, pp 183-211, summarizes the state of the art in the thermal and light-induced yellowing of lignin-containing pulps such as thermomechanical (TMP) and chemithermomechical (CTMP) pulps, showing the seriousness of these undesirable effects discusses generally the then current prior art methods used to attack this problem. These include bleaching, the use of phosphites, UV absorbers, polyalkylene glycols and free radical scavengers such as ascorbic acid, thiols, thioethers, dienes and aliphatic aldehydes and chelating agents such as ethylene-diaminetetraacetic acid (EDTA). The author concluded that, although much progress had been made, much still remains to be done before a successful and practical solution to this loss of brightness and undesirable yellowing of lignin-containing pulp and/or paper is found.
The instant invention described in detail below provides such a solution where the use of selected hindered amine nitroxides, hindered amine hydroxylamines or their salts in combination with selected UV absorbers and metal chelating agents is seen to prevent loss of brightness and to enhance resistance to yellowing in pulp or paper still containing lignin.
The addition of hydroxylamines or nitroxide free radicals to high-yield pulp paper either alone or in combinations with UV absorbers, metal chelating agents, fluorescent whitening agents and/or stabilizing polymers effectively achieves light and thermal stability which is similar to that found in papers made from kraft pulps.
Hydroxylamines and nitroxides are known to be efficient free radical traps and may limit the production of o-quinones; UV absorbers limit photochemistry in the underlying substrate to which they are applied, and ultimately reduce the production of free radicals. UV absorbers and nitroxides are each effective at stemming some of the free radical chemistry leading to paper yellowing when used singly. However, when they are used together, hydroxylamines or nitroxides and UV absorbers can effectively stop photochemical yellowing of lignin containing papers which are exposed 24 hours a day under ambient fluorecent lighting conditions for at least 200 days. Both of these types of stabilizers show enhanced inhibiting activity when combined with a metal chelating agent such diethylenetriaminepentaacetic acid, or polymeric inhibitors such as polyethylene glycol.
More particularly the instant invention pertains to a composition having reduced loss of brightness and enhanced resistance to yellowing which comprises
(a) a pulp or paper which still contains lignin, and
(b) an effective stabilizing amount of a hindered amine compound of formula I or II 
xe2x80x83where
G1 and G2 are independently alkyl of 1 to 4 carbon atoms or are together pentamethylene,
Z1 and Z2 are each methyl, or Z1 and Z2 together form a linking moiety which may additionally be substituted by an ester, ether, hydroxy, oxo, cyanohydrin, amide, amino, carboxy or urethane group,
E is oxyl, hydroxyl, hydrogen, alkyl, alkyl substituted by hydroxyl, oxo or carboxy or interrupted by oxygen or carboxy; alkenyl, alkynyl, cycloalkyl, cycloalkenyl, bicycloalkyl, alkoxy, alkoxy substituted by hydroxyl, oxo or carboxy or interrupted by oxygen or carboxy, cycloalkoxy, alkenyloxy, cycloalkenyloxy, aralkyl, aralkoxy, acyl, R(Cxe2x95x90O)Oxe2x80x94, RO(Cxe2x95x90O)Oxe2x80x94, RN(Cxe2x95x90O)Oxe2x80x94 or chloro, where R is an aliphatic or aromatic moiety,
X is an inorganic or organic anion, such as phosphate, phosphonate, carbonate, bicarbonate, nitrate, chloride, bromide, bisulfite, sulfite, bisulfate, sulfate, borate, formate, acetate, benzoate, citrate, oxalate, tartrate, acrylate, polyacrylate, fumarate, maleate, itaconate, glycolate, gluconate, malate, mandelate, tiglate, ascorbate, polymethacrylate, a carboxylate of nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, ethylenediaminetetraacetic acid or of diethylenetriaminepentaacetic acid, a diethylenetriaminepentamethylenephosphonate, an alkylsulfonate or an arylsulfonate, and
where the total charge of cations h is equal to the total charge of anions j, and with the proviso that the compound of formula I is not bis(2,2,6,6-tetramethylpiperidin-4-yl) sebacate or the polycondensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid.
Preferably, the compositions are those where in the compound of component (b), E is oxyl, hydroxyl, alkenyloxy, aralkoxy, alkyloxy or alkyl substituted by oxo or interrupted by carboxy, especially wherein E is oxyl or hydroxy; most especially wherein E is hydroxy.
Most preferably, X is chloride, bisulfite, bisulfate, sulfate, phosphate, nitrate, ascorbate, acetate, citrate or carboxylate of ethylenediaminetetraacetic acid or of diethylenetriaminepentaacetic acid; most especially wherein X is bisulfate or citrate.
Preferably, the hindered amine compounds of component (b) are those of formulas A to EE and A* to EE* 
wherein
E is oxyl, hydroxyl, hydrogen, alkyl of 1 to 18 carbon atoms, alkyl of 2 to 12 carbon atoms substituted by one to three hydroxyl or said alkyl interrupted by one to four oxygen atoms, or said alkyl both substituted by said hydroxyl groups and interrupted by said oxygen atoms, alkenyl of 2 to 18 carbon atoms, alkynyl of 2 to 12 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, cycloalkenyl of 5 to 12 carbon atoms, bicycloalkyl of 6 to 10 carbon atoms, alkoxy of 1 to 18 carbon atoms, alkoxy of 2 to 12 carbon atoms substituted by one to three hydroxyl groups or said alkoxy interrupted by one to four oxygen atoms or said alkoxy substituted by xe2x80x94COOZ where Z is hydrogen or alkyl of 1 to 4 carbon atoms, cycloalkoxy of 5 to 12 carbon atoms, cycloalkenyloxy of 5 to 12 carbon atoms, alkenyloxy of 2 to 18 carbon atoms, aralkyl of 7 to 15 carbon atoms, aralkoxy of 7 to 15 carbon atoms, alkanoyl of 2 to 12 carbon atoms, alkenoyl of 2 to 12 carbon atoms, benzoyl, or R(Cxe2x95x90O)Oxe2x80x94, RO(Cxe2x95x90O)Oxe2x80x94, RN(Cxe2x95x90O)Oxe2x80x94, where R is alkyl of 1 to 6 carbon atoms or phenyl,
R is hydrogen or methyl,
in formula A and A*,
n is 1 or 2,
when n is 1,
R1 is hydrogen, alkyl of 1 to 18 carbon atoms, alkenyl of 2-18 carbon atoms, propargyl, glycidyl, alkyl of 2 to 50 carbon atoms interrupted by one to twenty oxygen atoms, said alkyl substituted by one to ten hydroxyl groups or both interrupted by said oxygen atoms and substituted by said hydroxyl groups, or
R1 is alkyl of 1 to 4 carbon atoms substituted by a carboxy group or by xe2x80x94COOZ where Z is hydrogen, alkyl of 1 to 4 carbon atoms or phenyl, or where Z is said alkyl substituted by xe2x80x94(COOxe2x88x92)nMn+ where n is 1-3 and M is a metal ion from the 1st, 2nd or 3rd group of the periodic table or is Zn, Cu, Ni or Co, or M is a group Nn+(R2)4 where R2 is alkyl of 1 to 8 carbon atoms or benzyl,
when n is 2,
R1 is alkylene of 1 to 12 carbon atoms, alkenylene of 4 to 12 carbon atoms, xylylene or alkylene of 1 to 50 carbon atoms interrupted by one to twenty oxygen atoms, substituted by one to ten hydroxyl groups or both interrupted by said oxygen atoms and substituted by said hydroxyl groups,
in formula B and B*,
m is 1 to 4,
when m is 1,
R2 is alkyl of 1 to 18 carbon atoms, alkyl of 3 to 18 carbon atoms interrupted by xe2x80x94COOxe2x80x94, or R2 is xe2x80x94CH2(OCH2CH2)nOCH3 where n is 1 to 12, or
R2 is cycloalkyl of 5 to 12 carbon atoms, aryl of 6 to 12 carbon atoms, or said aryl substituted by one to four alkyl groups of 1 to 4 carbon atoms, or
R2 is xe2x80x94NHR3 where R3 is alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, aryl of 6 to 12 carbon atoms, or said aryl substituted by one to four alkyl of 1 to 4 carbon atoms, or
R2 is xe2x80x94NHR3 where R3 is alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, aryl of 6 to 12 carbon atoms, or said aryl substituted by one to four alkyl of 1 to 4 carbon atoms, or
R2 is xe2x80x94N(R3)2 where R3 is as defined above,
when m is 2,
R2 is alkylene of 1 to 12 carbon atoms, alkenylene of 4 to 12 carbon atoms, xylylene, alkylene of 2 to 12 carbon atoms interrupted by xe2x80x94COOxe2x80x94, or R2 is xe2x80x94CH2(OCH2CH2)nOCH2xe2x80x94 where n is 1 to 2, or
R2 is cycloalkylene of 5 to 12 carbon atoms, aralkylene of 7 to 15 carbon atoms or arylene of 6 to 12 carbon atoms, or
R2 is xe2x80x94NHR4NHxe2x80x94 where R4 is alkylene of 2 to 18 carbon atoms, cycloalkylene of 5 to 12 carbon atoms, aralkylene of 8 to 15 carbon atoms or arylene of 6 to 12 carbon atoms, or
R2 is xe2x80x94N(R3)R4N(R3)xe2x80x94 where R3 and R4 are as defined above, or
R2 is xe2x80x94COxe2x80x94 or xe2x80x94NHxe2x80x94COxe2x80x94NHxe2x80x94,
when m is 3,
R2 is alkanetriyl of 3 to 8 carbon atoms or benzenetriyl, or
when m is 4,
R2 is alkanetetrayl of 5 to 8 carbon atoms or benzenetetrayl,
in formula C and C*,
R10 is hydrogen, alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, aralkyl of 7 to 15 carbon atoms, alkanoyl of 2 to 18 carbon atoms, alkenoyl of 3 to 5 carbon atoms or benzoyl,
x is 1 or 2,
when x is 1,
R11 is hydrogen, alkyl of 1 to 18 carbon atoms, alkenyl of 2 to 18 carbon atoms, propargyl, glycidyl, alkyl of 2 to 50 carbon atoms interrupted by one to twenty oxygen atoms, said alkyl substituted by one to ten hydroxyl groups or both interrupted by said oxygen atoms and substituted by said hydroxyl groups, or
R11 is alkyl of 1 to 4 carbon atoms substituted by a carboxy group or by xe2x80x94COOZ where Z is hydrogen, alkyl of 1 to 4 carbon atoms or phenyl, or where Z is said alkyl substituted by xe2x80x94(COOxe2x88x92)nMn+ where n is 1-3 and M is a metal ion from the 1st, 2nd or 3rd group of the periodic table or is Zn, Cu, Ni or Co, or M is a group Nn+(R2)4 where R2 is hydrogen, alkyl of 1 to 8 carbon atoms or benzyl, or
when x is 2,
R11 is alkylene of 1 to 12 carbon atoms, alkenylene of 4 to 12 carbon atoms, xylylene or alkylene of 1 to 50 carbon atoms interrupted by one to twenty oxygen atoms, substituted by one to ten hydroxyl groups or both interrupted by said oxygen atoms and substituted by said hydroxyl groups,
in formula D and D*,
R10 is as defined above,
y is 1 to 4, and
R12 is defined as R2 above, in formula E and E*,
k is 1 or 2,
when k is 1,
R20 and R2, are independently alkyl of 1 to 12 carbon atoms, alkenyl of 2 to 12 carbon atoms or aralkyl of 7 to 15 carbon atoms, or R20 is also hydrogen, or
R20 and R21 together are alkylene of 2 to 8 carbon atoms or said alkylene substituted by hydroxyl, or are acyloxy-alkylene of 4 to 22 carbon atoms, or
when k is 2
R20 and R21 are together (xe2x80x94CH2)2C(CH2xe2x80x94)2,
in formula F and F*,
R30 is hydrogen, alkyl of 1 to 18 carbon atoms, benzyl, glycidyl, or alkoxyalkyl of 2 to 6 carbon atoms,
g is 1 or 2,
when g is 1, R31 is defined as R1 above when n is 1,
when g is 2, R31 is defined as R1 above when n is 2,
in formula G and G*,
Q1 is xe2x80x94NR41xe2x80x94 or xe2x80x94Oxe2x80x94,
E1 is alkylene of 1 to 3 carbon atoms, or E1 is xe2x80x94CH2xe2x80x94CH(R42)xe2x80x94Oxe2x80x94 where R42 is hydrogen, methyl or phenyl, or E1 is xe2x80x94(CH2)3xe2x80x94NHxe2x80x94 or E1 is a direct bond,
R40 is hydrogen or alkyl of 1 to 18 carbon atoms,
R41 is hydrogen, alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, aralkyl of 7 to 15 carbon atoms, aryl of 6 to 10 carbon atoms, or R41 is xe2x80x94CH2xe2x80x94CH(R42)xe2x80x94OH where R42 is as defined above,
in formula H and H*,
p is1 or 2,
T4 is as defined for R11 when x is 1 or 2,
M and Y are independently methylene or carbonyl, preferably M is methylene and Y is carbonyl,
in formula I and I*,
this formula denotes a recurring structural unit of a polymer where T1 is ethylene or 1,2-propylene or is the repeating structural unit derived from an alpha-olefin copolymer with an alkyl acrylate or methacrylate, and where
q is 2 to 100,
Q1 is xe2x80x94N(R41)xe2x80x94 or xe2x80x94Oxe2x80x94 where R41 is as defined above,
in formula J and J*,
r is 1 or 2,
T7 is as defined for R1 when n is 1 or 2 in formula A,
preferably T7 is octamethylene when r is 2,
in formula L and L*,
u is 1 or 2,
T13 is as defined for R1 when n is 1 or 2 in formula A, with the proviso that T13 is not hydrogen when u is 1,
in formula M and M*,
E1 and E2, being different, each are xe2x80x94COxe2x80x94 or xe2x80x94N(E5)xe2x80x94where E5 is hydrogen, alkyl of 1 to 12 carbon atoms or alkoxycarbonylalkyl of 4 to 22 carbon atoms, preferably E1 is xe2x80x94COxe2x80x94 and E2 is xe2x80x94N(E5)xe2x80x94,
E3 is hydrogen, alkyl of 1 to 30 carbon atoms, phenyl, naphthyl, said phenyl or said naphthyl substituted by chlorine or by alkyl of 1 to 4 carbon atoms, or phenylalkyl of 7 to 12 carbon atoms, or said phenylalkyl substituted by alkyl of 1 to 4 carbon atoms,
E4 is hydrogen, alkyl of 1 to 30 carbon atoms, phenyl, naphthyl or phenylalkyl of 7 to 12 carbon atoms, or
E3 and E4 together are polymethylene of 4 to 17 carbon atoms, or said polymethylene substituted by one to four alkyl of 1 to 4 carbon atoms, preferably methyl,
in formula N,
R1 is as defined for R1 in formula A when n is 1,
G3 is a direct bond, alkylene of 1 to 12 carbon atoms, phenylene or xe2x80x94NHxe2x80x94G1xe2x80x94NHxe2x80x94 where G1 is alkylene of 1 to 12 carbon atoms,
in formula O and O*,
R10 is as defined for R10 in formula C,
in formula P and P*,
E6 is an aliphtic or aromatic tetravalent radical, preferably neopentanetetrayl or benzenetetrayl,
in formula T and T*,
R51 is hydrogen, alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, or aryl of 6 to 10 carbon atoms,
R52 is hydrogen or alkyl of 1 to 18 carbon atoms, or
R51 and R52 together of alkylene of 4 to 8 carbon atoms,
f is 1 or 2,
when f is 1,
R50 is as defined for R11 in formula C when x is 1, or R50 is xe2x80x94(CH2)zCOOR54 where z is 1 to 4 and R54 is hydrogen or alkyl of 1 to 18 carbon atoms, or R54 is a metal ion from the 1st, 2nd or 3rd group of the periodic table or a group xe2x80x94N(R55)4 where R55 is hydrogen, alkyl of 1 to 12 carbon atoms or benzyl,.
when f is 2, R50 is as defined for R11 in formula C when x is 2,
in formula U and U*,
R53, R54, R55 and R56 are independently alkyl of 1 to 4 carbon atoms or are together pentamethylene.
in formula V and V*,
R57, R58, R59 and R60 are independently alkyl of 1 to 4 carbon atoms or are together pentamethylene.
in formula W and W*,
R61, R62, R63 and R64 are independently alkyl of 1 to 4 carbon atoms or are together pentamethylene,
R65 is alkyl of 1 to 5 carbon atoms,
M is hydrogen or oxygen,
wherein in formulas X to CC and X* to CC*
n is 2 to 3,
G1 is hydrogen, methyl, ethyl, butyl or benzyl,
m is 1 to 4,
x is 1 to 4,
when x is 1, R1 and R2 are independently alkyl of 1 to 18 carbon atoms, said alkyl interrupted by one to five oxygen atoms, said alkyl substituted by 1 to 5 hydroxyl groups or said alkyl both interrupted by said oxygen atoms and substituted by said hydroxyl groups; cycloalkyl of 5 to 12 carbon atoms, aralkyl of 7 to 15 carbon atoms, aryl of 6 to 10 carbon atoms or said aryl substituted by one to three alkyl of 1 to 8 carbon atoms, or R1 is also hydrogen,
or R1 and R2 are together tetramethylene, pentamethylene, hexamethylene or 3-oxapentamethylene,
when x is 2,
R1 is hydrogen, alkyl of 1 to 8 carbon atoms, said alkyl interrupted by one or two oxygen atoms, said alkyl substituted by a hydroxyl group, or said alkyl both interrupted by one or two oxygen atoms and substituted by a hydroxyl group,
R2 is alkylene of 2 to 18 carbon atoms, said alkylene interrupted by one to five oxygen atoms, said alkylene substituted by 1 to 5 hydroxyl groups or said alkylene both interrupted by said oxygen atoms and substituted by said hydroxyl groups; o-, m- or p-phenylene or said phenylene substituted by one or two alkyl of 1 to 4 carbon atoms, or
R2 is xe2x80x94(CH2)kO[(CH2)kO]h(CH2)kxe2x80x94 where k is 2 to 4 and h is 1 to 40, or
R1 and R2 together with the two N atoms to which they are attached are piperazin-1,4-diyl,
when x is 3,
R1 is hydrogen,
R2 is alkylene of 4 to 8 carbon atoms interrupted by one nitrogen atom,
when x is 4,
R1 is hydrogen,
R2 is alkylene of 6 to 12 carbon atoms interrupted by two nitrogen atoms,
R3 is hydrogen, alkyl of 1 to 8 carbon atoms, said alkyl interrupted by one or two oxygen atoms, said alkyl substituted by a hydroxyl group, or both interrupted by one or two oxygen atoms and substituted by a hydroxyl group,
p is 2 or 3, and
Q is an alkali metal salt, ammonium or N+(G1)4,
in formula DD and DD*
m is 2 or 3,
when m is 2, G is xe2x80x94(CH2CHRxe2x80x94O)rCH2CHRxe2x80x94, where r is 0 to 3, and R is hydrogen or methyl, and
when m is 3, G is glyceryl,
in formula EE and EE*
G2 is xe2x80x94CN, xe2x80x94CONH2 or xe2x80x94COOG3 where G3 is hydrogen, alkyl of 1 to 18 carbon atoms or phenyl,
X is an inorganic or organic anion, such as phosphate, phosphonate, carbonate, bicarbonate, nitrate, chloride, bromide, bisulfite, sulfite, bisulfate, sulfate, borate, formate, acetate, benzoate, citrate, oxalate, tartrate, acrylate, polyacrylate, fumarate, maleate, itaconate, glycolate, gluconate, malate, mandelate, tiglate, ascorbate, polymethacrylate, a carboxylate of nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, ethylenediaminetetraacetic acid or of diethylenetriaminepentaacetic acid, a diethylenetriaminepentamethylenephosphonate, an alkylsulfonate or an arylsulfonate, and
where the total charge of cations h is equal to the total charge of anions j, and with the proviso that bis(2,2,6,6-tetramethylpiperidin-4-yl) sebacate or the polycondensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid are excluded.
Most preferably, the compounds of component (b) are those of formulas A, A*, B, B*, C, C*, D, D*, Q, Q*, R, R*, S, S*, X, X*, Y, Y*, Z and Z*,
where E is oxyl or hydroxyl,
R is hydrogen,
in formula A and A*
n is 1 or 2,
when n is 1,
R1 is hydrogen, alkyl of 1 to 6 carbon atoms, alkenyl of 2-6 carbon atoms, propargyl, glycidyl, alkyl of 2 to 20 carbon atoms interrupted by one to ten oxygen atoms, said alkyl substituted by one to five hydroxyl groups or both interrupted by said oxygen atoms and substituted by said hydroxyl groups, or
R1 is alkyl of 1 to 4 carbon atoms substituted by a carboxy group or by xe2x80x94COOZ where Z is hydrogen or alkyl of 1 to 4 carbon atoms,
when n is 2,
R1 is alkylene of 1 to 8 carbon atoms, alkenylene of 4 to 8 carbon atoms, alkylene of 1 to 20 carbon atoms interrupted by one to ten oxygen atoms, substituted by one to five hydroxyl groups or both interrupted by said oxygen atoms and substituted by said hydroxyl groups,
in formula B and B*
m is 1 or 2
when m is 1,
R2 is alkyl of 1 to 4 carbon atoms or R2 is CH2(OCH2CH2)nOCH3 where n is 1 to 12, or
R2 is phenyl, or said phenyl substituted by one to three methyl groups,
R2 is xe2x80x94NHR3 where R3 is alkyl of 1 to 4 carbon atoms or phenyl, or said phenyl substituted by one or two methyl groups,
when m is 2,
R2 is alkylene of 1 to 8 carbon atoms, alkenylene of 4 to 8 carbon atoms, or R2 is xe2x80x94CH2(OCH2CH2)nOCH2xe2x80x94 where n is 1 to 12,
R2 is NHR4NH where R4 is of 2 to 6 carbon atoms, aralkylene of 8 to 15 carbon atoms or arylene of 6 to 12 carbon atoms,
R2 is xe2x80x94COxe2x80x94 or xe2x80x94NHCONH,
in formula C and C*,
R10 is hydrogen or, alkanoyl of 1 to 3 carbon atoms,
x is 1 or 2,
when x is 1,
R11 is hydrogen, alkyl of 1 to 6 carbon atoms or glycidyl,
R11 is alkyl of 1 to 4 carbon atoms substituted by a carboxy group or by COOZ where Z is hydrogen or alkyl of 1 to 4 carbon atoms,
when x is 2,
R11 is alkylene of 1 to 6 carbon atoms,
in formula D and D*,
R10 is hydrogen,
y is 1 or 2,
R12 is defined as R2 above,
in formula Y, Y*, Z and Z*,
x is 1 or 2,
when x is 1,
R1 and R2 are independently alkyl of 1 to 4 carbon atoms,
or R1 and R2 are together tetramethylene, or pentamethylene,
R2 is hydrogen or alkyl of 1 to 4 carbon atoms, said alkyl group substituted by a hydroxyl group,
when x is 2,
R1 is hydrogen, alkyl of 1 to 4 carbon atoms, said alkyl substituted by a hydroxyl group,
R2 is alkylene of 2 to 6 carbon atoms,
R3 is as defined above.
Especially preferred, the compounds of component (b) are those of formulas A, A*, B, B*, C, C*, D, D*, Q, Q*, R and R*,
where E is oxyl or hydroxyl,
R is hydrogen,
in formula A and A*,
h is 1,
R1 is hydrogen, alkyl of 1 to 4 carbon atoms, glycidyl, alkyl of 2 to 4 carbon atoms interrupted by one or two oxygen atoms, said alkyl substituted by one or two hydroxyl groups or both interrupted by said oxygen atoms and substituted by said hydroxyl groups, or
R1 is alkyl of 1 to 4 carbon atoms substituted by xe2x80x94COOZ where Z is hydrogen or alkyl of 1 to 4 carbon atoms,
in formula B and B*,
m is 1 or 2,
R2 is alkyl of 1 to 4 carbon atoms or R2 is CH2(OCH2CH2)nOCH3 where n is 1 to 4,
when m is 2,
R2 is alkylene of 1 to 8 carbon atoms,
in formula C and C*,
R10 is hydrogen or alkanoyl of 1 or 2 carbon atoms,
x is 1 or 2,
when x is 1,
R11 is hydrogen, alkyl of 1 to 4 carbon atoms or glycidyl,
R11 is alkyl of 1 to 4 carbon atoms substituted by COOZ where Z is hydrogen or alkyl of 1 to 4 carbon atoms,
when x is 2,
R11 is alkylene of 1 to 6 carbon atoms,
in formula D and D*,
R10 is hydrogen,
y is 1 or 2,
R12 is defined as R2 above.
More particularly, the hindered amine compound is
(a) bis(1-oxyl-2,2-6-6-tetramethylpiperidin-4-yl) sebacate;
(b) bis(1-hydroxy-2,2-6-6-tetramethylpiperidin-4-yl) sebacate;
(c) 1-hydroxy-2,2-6-6-tetramethyl-4-acetoxypiperidinium citrate;
(d) 1-oxyl-2,2,6,6-tetramethyl4-acetamidopiperidine;
(e) 1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidine;
(f) 1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium bisulfate;
(g) 1-oxyl-2,2,6,6-tetramethyl-4-oxo-piperidine;
(h) 1-hydroxy -2,2,6,6-tetramethyl-4-oxo-piperidine;
(i) 1-hydroxy -2,2,6,6-tetramethyl-4-oxo-piperidinium acetate;
(j) 1-oxyl-2,2,6,6-tetramethyl-4-methoxy-piperidine;
(k) 1-hydroxy-2,2,6,6-tetramethyl-4-methoxy-piperidine;
(I) 1-hydroxyl-2,2,6,6-tetramethyl-4-methoxy-piperidinium acetate;
(m) 1-oxyl-2,2,6,6-tetramethyl-4-acetoxypiperidine;
(n) 1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidine;
(o) 1-oxyl-2,2,6,6-tetramethyl-4-propoxy-piperidine;
(p) 1-hydroxy-2,2,6,6-tetramethyl-4-propoxy-piperidinium acetate;
(q) 1-hydroxy-2,2,6,6-tetramethyl-4-propoxy-piperidine;
(r) 1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy4-oxapentoxy)piperidine;
(s) 1-hydroxy-2,2,6,6-tetramethyl-4-(2-hydroxy-4-oxapentoxy)piperidinium acetate;
(t) 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine;
(u) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidine;
(v) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium chloride;
(w) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium acetate;
(x) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium bisulfate;
(y) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium citrate;
(z) bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) citrate;
(aa) tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) citrate.
(bb) tetra(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) ethylenediaminetetraacetic;
(cc) tetra(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) ethylenediaminetetraacetate;
(dd) tetra(1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidinium) ethylenediaminetetraacetate;
(ee) penta(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) diethylenetriaminepentaacetate;
(ff) penta(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) diethylenetriaminepentaacetate;
(gg) penta(1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidinium) diethylenetriaminepentaacetate;
(hh) tri(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) nitrilotriacetate;
(ii) tri(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) nitrilotriacetate;
(jj) tri(1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidinium) nitrilotriacetate;
(kk) penta(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) diethylenetriaminepentamethylenephosphonate;
(ll) penta(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) diethylenetriaminepentamethylenephosphonate;
(mm) penta(1-hydroxy-2,2,6 ,6-tetramethyl-4-oxopiperidinium) diethylenetriaminepentamethylenephosphonate.
Most especially, the hindered amine compound is
(a) 1-oxyl-2,2,6,6-tetramethyl4-hydroxypiperidine;
(b) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidine;
(c) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium chloride;
(d) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium acetate;
(e) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium bisulfate;
(f) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium citrate;
(g) bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) citrate;
(h) tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) citrate;
(i) tetra(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) ethylenediaminetetraacetate;
(j) tetra(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) ethylenediaminetetraacetate;
(k) tetra(1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidinium) ethylenediaminetetraacetate;
(l) penta(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) diethylenetriaminepentaacetate;
(m) penta(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) diethylenetriaminepentaacetate;
(n) penta(1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidinium) diethylenetriaminepentaacetate.
The instant compositions may additionally include an effective amount of at least one coadditive selected from the group consisting of the UV absorbers, the polymeric inhibitors, the sulfur containing inhibitors, the phosphorus containing compounds, the nitrones, the benzofuran-2-ones and the hydroxylamines and mixtures thereof.
The compositions which also include a UV absorber are especially preferred. The UV absorber is selected from group consisting of the benzotriazoles, the s-triazines, the benzophenones, the xcex1-cyanoacrylates, the oxanilides, the benzoxazinones, the benzoates and the xcex1-alkyl cinnamates.
Preferably, the UV absorber is a benzotriazole, an s-triazine or a benzophenone, most especially a benzotriazole UV absorber or benzophenone UV absorber.
Typical and useful UV absorbers are, for example,
(a) 5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole;
(b) 2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole;
(c) 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole;
(d) 2-(2-hydroxy-3,5-di-xcex1-cumylphenyl)-2H-benzotriazole;
(e) 2-(2-hydroxy-3-xcex1-cumyl-5-tert-octylphenyl)-2H-benzotriazole;
(f) 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole;
(g) 3-(2H-benzotriazol-2-yl)-4-hydroxy-5-(1-methylpropyl)-benzenesulfonic acid monosodium salt;
(h) 3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamic acid and sodium salt;
(i) 12-hydroxy-3,6,9-trioxadodecyl 3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)hydrocinnamate;
(j) octyl 3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamate;
(k) 4,6-bis(2,4-dimethylphenyl)-2-(4-(3-dodecyloxy*-2-hydroxypropoxy)-2-hydroxy phenyl)-s-triazine (*is mixture of C12-14oxy isomers);
(l) 4,6-bis(2,4-dimethylphenyl)-2-(4-octyloxy-2-hydroxyphenyl)-s-triazine;
(m) 2,4-dihydroxybenzophenone;
(n) 2,2xe2x80x2-dihydroxy-4,4xe2x80x2-dimethoxy-5,5xe2x80x2-disulfobenzophenone, disodium salt;
(o) 2-hydroxy-4-octyloxybenzophenone;
(p) 2-hydroxy-4-dodecyloxybenzophenone;
(q) 2,4-dihydroxybenzophenone;
(r) 2,2xe2x80x2,4,4xe2x80x2-tetrahydroxybenzophenone;
(s) 4-aminobenzoic acid;
(t) 2,3-dihydroxypropyl-4-aminobenzoic acid;
(u) 3-(4-imidazolyl)acrylic acid;
(v) 2-phenyl-5-benzimidazole sulfonic acid;
(w) N,N,N-trimethyl-xcex1-(2-oxo-3-bornylidene)-p-toluidinium methyl sulfate;
(x) 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid, sodium salt;
(y) 3-(4-benzoyl-3-hydroxyphenoxy)-2-hydroxy-N,N,N-trimethyl-1-propanaminium chloride;
(z) 3-[4-(2H-benzotriazol-2-yl)-3-hydroxyphenoxy]-2-hydroxy-N,N,N-trimethyl-1-propanaminium, chloride;
(aa) 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole; and
(bb) 2,2xe2x80x2-dihydroxy-4,4xe2x80x2-dimethoxybenzophenone (Uvinul(copyright) 3049).
Preferred UV absorbers are
(a) 3-(2H-benzotriazol-2-yl)-4-hydroxy-5-(1-methylpropyl)-benzenesulfonic acid monosodium salt;
(b) 3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamic acid and sodium salt;
(c)2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole;
(d) 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole;
(e) 4,6-bis(2,4-dimethylphenyl)-2-(4-(3-dodecyloxy*-2-hydroxypropoxy)-2-hydroxy phenyl)-s-triazine (*is mixture of C12-14oxy isomers);
(f) 12-hydroxy-3,6,9-trioxadodecyl 3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)hydrocinnamate;
(g) 2,4-dihydroxybenzophenone;
(h) 2,2xe2x80x2-dihydroxy-4,4xe2x80x2-dimethoxy-5,5xe2x80x2-disulfobenzophenone, disodium salt;
(i) 2,2xe2x80x2,4,4xe2x80x2-tetrahydroxybenzophenone;
(j)3-(4-benzoyl-3-hydroxyphenoxy)-2-hydroxy-N,N,N-trimethyl-1-propanaminium chloride;
(k) 3-[4-(2H-benzotriazol-2-yl)-3-hydroxyphenoxy]-2-hydroxy-N,N,N-trimethyl-1-propanaminium, chloride;
(l) 5-benzoyl-4-hydroxy-2-methoxy-benzenesulfonic acid, sodium salt
(m) 2-(2-hydroxy-3-xcex1-cumyl-5-tert-octylphenyl)-2H-benzotriazole.
Other preferred compositions are those which additionally contain a metal chelating agent, i.e. those that offer thermodynamic or kinetic control of metal ions. Examples kinetic controlling chelating agents are citrates, keto acids, gluconates, heptagluconates, phosphates, and phosphonates. Examples of chelating agents that offer thermodynamic control are the aminocarboxylic acid chelates. Well known and commercially available members of this class include ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), nitrilotriacetic acid (NTA) and diethylenetriaminepentamethylenephosphonic acid (DTPMPA).
Still other preferred compositions are those which contain mixtures of thermodynamic and kinetic controlling chelating agents are also preferred.
Still other preferred compositions are those which additionally contain a polymeric inhibitor; preferably poly(ethylene glycol) (PEO), poly(propylene glycol) (PPO), poly(butylene glycol) (PTHF), poly(vinyl pyrrolidone) (PVP) or thiol-capped poly(ethylene glycol) as well as copolymers such as poly(ethylene/propylene glycol).
Still other preferred compositions are those which additional contain a fluorescent whitening agent selected from a wide range of chemical types such as 4,4xe2x80x2-bis-(triazinylamino)-stilbene-2,2xe2x80x2-disulfonic acids, 4,4xe2x80x2-bis-(triazol-2-yl)stilbene-2,2xe2x80x2-disulfonic acids, 4,4xe2x80x2-dibenzofuranyl-biphenyls, 4,4xe2x80x2-(diphenyl)-stilbenes, 4,4xe2x80x2-distyryl-biphenyls, 4-phenyl4xe2x80x2-benzoxazolyl-stilbenes, stilbenyl-naphthotriazoles, 4-styryl-stilbenes, bis-(benzoxazol-2-yl) derivatives, bis-(benzimidazol-2-yl) derivatives, coumarins, pyrazolines, naphthalimides, triazinyl-pyrenes, 2-styryl-benzoxazole or -naphthoxazoles, benzimidazole-benzofurans or oxanilides.
Some preferred compositions contain a mixture of additional stabilizers such as a mixture of a UV absorber and polymeric inhibitor; or a mixture of a UV absorber and a metal chelating agent; or a mixture of a polymeric inhibitor and a metal chelating agent; or a mixture of a polymeric inhibitor and a fluorescent whitening agent; or a mixture of a fluorescent whitening agent and a metal chelating agent; or a mixture of a UV absorber, metal chelating agent and a polymeric inhibitor; or a mixture of fluorescent whitening agent, metal chelating agent and polymeric inhibitor.
Preferably the compositions are those wherein the compound of formula I or II is of low molecular weight or contains hydrophilic moieties especially cationic groups, is both of low molecular weight and contains hydrophilic moieties.
The instant invention also pertains to a process for preventing the loss of brightness and for enhancing resistance to yellowing of chemimechanical or thermomechanical pulp or paper which still contains lignin, which comprises
Treating said pulp or paper with an effective stabilizing amount of a compound of formula I or II, preferably a compound of formula A to EE or A* to EE* as described above.
Preferably the process is that where in the compound of formula A to EE or A* to EE*, E is oxyl or hydroxyl and most preferably E is hydroxyl.
The instant invention also pertains to new compounds of formula IV, V, VI, VII or VIII 
wherein
n is 2 to 3,
G1 is hydrogen, methyl, ethyl, butyl or benzyl,
X is an inorganic or organic anion, such as phosphate, phosphonate, carbonate, bicarbonate, nitrate, chloride, bromide, bisulfite, sulfite, bisulfate, sulfate, borate, formate, acetate, benzoate, citrate, oxalate, tartrate, acrylate, polyacrylate, fumarate, maleate, itaconate, glycolate, gluconate, malate, mandelate, tiglate, ascorbate, polymethacrylate, a carboxylate of nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, ethylenediaminetetraacetic acid or of diethylenetriaminepentaacetic acid, a diethylenetriaminepentamethylenephosphonate, an alkylsulfonate or an arylsulfonate,
m is 1 to 4,
x is 1 to 4,
when x is 1, R1 and R2 are independently alkyl of 1 to 18 carbon atoms, said alkyl interrupted by one to five oxygen atoms, said alkyl substituted by 1 to 5 hydroxyl groups or said alkyl both interrupted by said oxygen atoms and substituted by said hydroxyl groups; cycloalkyl of 5 to 12 carbon atoms, aralkyl of 7 to 15 carbon atoms, aryl of 6 to 10 carbon atoms or said aryl substituted by one to three alkyl of 1 to 8 carbon atoms, or R1 is also hydrogen,
or R1 and R2 are together tetramethylene, pentamethylene, hexamethylene or 3-oxapentamethylene,
when x is 2,
R1 is hydrogen, alkyl of 1 to 8 carbon atoms, said alkyl interrupted by one or two oxygen atoms, said alkyl substituted by a hydroxyl group, or said alkyl both interrupted by one or two oxygen atoms and substituted by a hydroxyl group,
R2 is alkylene of 2 to 18 carbon atoms, said alkylene interrupted by one to five oxygen atoms, said alkylene substituted by 1 to 5 hydroxyl groups or said alkylene both interrupted by said oxygen atoms and substituted by said hydroxyl groups; o-, m- or p-phenylene or said phenylene substituted by one or two alkyl of 1 to 4 carbon atoms, or
R2 is xe2x80x94(CH2)kO[(CH2)kO]h(CH2)kxe2x80x94 where k is 2 to 4 and h is 1 to 40, or
R1 and R2 together with the two N atoms to which they are attached are piperazin-1,4-diyl,
when x is 3,
R1 is hydrogen,
R2 is alkylene of 4 to 8 carbon atoms interrupted by one nitrogen atom,
when x is 4,
R1 is hydrogen,
R2 is alkylene of 6 to 12 carbon atoms interrupted by two nitrogen atoms,
R3 is hydrogen, alkyl of 1 to 8 carbon atoms, said alkyl interrupted by one or two oxygen atoms, said alkyl substituted by a hydroxyl group, or both interrupted by one or two oxygen atoms and substituted by a hydroxyl group,
p is2or3, and
Q is an alkali metal salt, ammonium or N+(G1)4.
Preferably, in the compounds of formulas IV to VIII
n is 2; G1 is hydrogen or methyl; X is chloro or bromo; x is 1 or 2, R1 and R2 are independently alkyl of 1 to 8 carbon atoms, said alkyl interrupted by one or two oxygen atoms, said alkyl substituted by a hydroxyl group, or said alkyl both interrupted by one or two oxygen atoms and substituted by a hydroxyl group, or R1 is hydrogen; or R1 and R2 together are 3-oxa-pentamethylene; R3 is hydrogen or alkyl of 1 to 2 carbon atoms, or said alkyl substituted by a hydroxyl group, p is 2, m is 1, and Q is Na+, NH4+ or N(CH3)4+.
Typical compounds falling within the structures of formulas IV to VIII and which are useful in this invention are:
(a) 1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-4-oxa-6-trimethylammmoniumhexyloxy)piperidine chloride;
(b) 1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-3-trimethylammoniumpropoxy)piperidine chloride;
(c) 1-oxyl-2,2,6,6-tetramethyl-4-{2-hydroxy-3-[di(2-hydroxyethyl)amino]propoxy}piperidine;
(d) 1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-3-dimethylaminopropoxy)piperidine;
(e) 1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-3-diethylaminopropoxy)piperidine;
(f) N,Nxe2x80x2-dimethyl-N,Nxe2x80x2-bis-[3-(1-oxyl-2,2,6,6-tetramethyl-piperidin-4-yloxy)-2-hydroxypropyl]hexamethylenediamine;
(g) N,N,Nxe2x80x2,Nxe2x80x2-tetramethyl-N,Nxe2x80x2-bis-[3-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yloxy)-2-hydroxypropyl]-hexamethylenediammonium dibromide;
(h) 1-oxyl-2,2,6,6-tetramethyl-4-[2-hydroxy-3-(N,N-dimethyl-N-propylammonium)propoxy]piperidine chloride;
(i) sodium 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yloxyacetate; or
(j) 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yloxyacetic acid, choline ester.
The instant invention also pertains to novel hydroxylamine salts of formulae A*, D*, X*, Y*, Z*, M*, BB*, CC* and DD*, 
wherein
R is hydrogen,
in formula A*
n is 1,
R1 is hydrogen or alkyl of 1 to 4 carbon atoms, preferably hydrogen,
in formula D*
y is 1,
R10 is hydrogen or methyl, preferably hydrogen,
R12 is alkyl of 1 to 4 carbon atoms, preferably methyl,
X is phosphate, phosphonate, carbonate, bicarbonate, nitrate, chloride, bromide, bisulfite, sulfite, bisulfate, sulfate, borate, formate, acetate, benzoate, citrate, oxalate, tartrate, acrylate, polyacrylate, fumarate, maleate, itaconate, glycolate, gluconate, malate, mandelate, tiglate, ascorbate, polymethacrylate, a carboxylate of nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, ethylenediaminetetraacetic acid or of diethylenetriaminepentaacetic acid, a diethylenetriaminepentamethylenephosphonate, an alkylsulfonate or an arylsulfonate,
where the total charge of cations h is equal to the total charge of anions j,
wherein in formulas X* to DD*
n is 2 to 3,
G1 is hydrogen, methyl, ethyl, butyl or benzyl,
m is 1 to 4,
x is 1 to 4,
when x is 1, R1 and R2 are independently alkyl of 1 to 18 carbon atoms, said alkyl interrupted by one to five oxygen atoms, said alkyl substituted by 1 to 5 hydroxyl groups or said alkyl both interrupted by said oxygen atoms and substituted by said hydroxyl groups; cycloalkyl of 5 to 12 carbon atoms, aralkyl of 7 to 15 carbon atoms, aryl of 6 to 10 carbon atoms or said aryl substituted by one to three alkyl of 1 to 8 carbon atoms, or R1 is also hydrogen,
or R1 and R2 are together tetramethylene, pentamethylene, hexamethylene or 3-oxapentamethylene,
when x is 2,
R1 is hydrogen, alkyl of 1 to 8 carbon atoms, said alkyl interrupted by one or two oxygen atoms, said alkyl substituted by a hydroxyl group, or said alkyl both interrupted by one or two oxygen atoms and substituted by a hydroxyl group,
R2 is alkylene of 2 to 18 carbon atoms, said alkylene interrupted by one to five oxygen atoms, said alkylene substituted by 1 to 5 hydroxyl groups or said alkylene both interrupted by said oxygen atoms and substituted by said hydroxyl groups; o-, m- or p-phenylene or said phenylene substituted by one or two alkyl of 1 to 4 carbon atoms, or
R2 is xe2x80x94(CH2)kO[(CH2)kO]h(CH2)kxe2x80x94 where k is 2 to 4 and h is 1 to 40, or
R1 and R2 together with the two N atoms to which they are attached are piperazin-1,4-diyl,
when x is 3,
R1 is hydrogen,
R2 is alkylene of 4 to 8 carbon atoms interrupted by one nitrogen atom,
when x is 4,
R1 is hydrogen,
R2 is alkylene of 6 to 12 carbon atoms interrupted by two nitrogen atoms,
R3 is hydrogen, alkyl of 1 to 8 carbon atoms, said alkyl interrupted by one or two oxygen atoms, said alkyl substituted by a hydroxyl group, or both interrupted by one or two oxygen atoms and substituted by a hydroxyl group,
p is 2 or 3, and
Q is an alkali metal salt, ammonium or N+(G1)4,
in formula DD and DD*
m is2 or 3,
when m is 2, G is xe2x80x94(CH2CHRxe2x80x94O)rCH2CHRxe2x80x94, where r is 0 to 3, and R is hydrogen or methyl, and
when m is 3, G is glyceryl,
with the proviso that in formula A* when R1 is hydrogen, X is not chloride or bisulfate, and when in formula D* when R10 is hydrogen and R12 is methyl, X is not chloride or bisulfate.
Preferably, X is chloride, bisulfate, bisulfite, sulfate, nitrate, acetate, citrate or carboxylate of ethylenediaminetetraacetic acid or diethylenetriaminepentaacetic acid; most preferably, X is bisulfate or citrate.
Hydroxylamine salts of particular interest are
(a) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium citrate;
(b) bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)citrate;
(c) tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)citrate;
(d) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium DTPA;
(e) bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)DTPA;
(f) tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)DTPA;
(g) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)DTPA;
(h) pentakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)DTPA;
(i) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium EDTA;
(j) bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)EDTA;
(k) tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)EDTA;
(l) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)EDTA;
(m) 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium citrate;
(n) bis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium)citrate;
(o) tris(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium)citrate;
(p) 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium DTPA;
(q) bis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium)DTPA;
(r) tris(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium)DTPA;
(s) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium)DTPA;
(t) pentakis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium)DTPA;
(u) 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium EDTA;
(v) bis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium)EDTA;
(w) tris(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium)EDTA;
(x) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium)EDTA;
(y) 1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium citrate;
(z) bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)citrate;
(aa) tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)citrate;
(bb) 1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium DTPA;
(cc) bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)DTPA;
(dd) tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)DTPA;
(ee) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)DTPA;
(ff) pentakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)DTPA;
(gg) 1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium EDTA;
(hh) bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)EDTA;
(ii) tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)EDTA;
(jj) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)EDTA;
(kk) 1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium citrate;
(II) bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium)citrate;
(mm) tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium)citrate;
(nn) 1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium DTPA;
(oo) bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium)DTPA;
(pp) tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium)DTPA;
(qq) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium)DTPA;
(rr) pentakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium)DTPA;
(ss) 1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium EDTA;
(tt) bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium)EDTA;
(uu) tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium)EDTA or
(vv) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium)EDTA.
Nitroxides, hydroxylamines and their salts alone or in combination with UV absorbers are also effective in improving the resistance to yellowing of mechanical pulps which have been modified by acylation, alkylation, treatment with sodium borohydride or hydrogenated.
The intermediates needed to make the instant compounds are largely items of commerce.
The effective stabilizing amounts of the hindered amine is 0.001 to 5% by weight based on the pulp or paper. Preferably, the effective stabilizing amount is 0.005 to 2% by weight; preferably 0.01 to 1% by weight.
When a coadditive is also present, the effective amount of the coadditives is also 0.001 to 5% by weight based on the pulp or paper; preferably 0.005 to 2% by weight; most preferably 0.01 to 2% by weight.
The instant inhibitor additive system can be added to pulp or paper at a number of places during the manufacturing or processing operations. These include
a. on a pulp slurry in the latency chest;
b. on a pulp slurry in or after the bleaching stage in a storage, blending or transfer chest;
c. on pulp during or after bleaching, washing and dewatering followed by cylinder or flash drying;
d. before or after the cleaners;
e. before or after the fan pump to the paper machine headbox;
f. to the paper machine white water;
g. to the silo or save all;
h. in the press section using a size press, coater or spray bar;
i. in the drying section using a size press, coater or spray bar;
j. on the calender using a wafer box;
k. on paper in an off-machine coater or size press; and/or.
l. in the curl control unit.
Clearly, the precise location where the stabilizer additives should be added will depend on the specific equipment involved, the exact process conditions being used and the like. In some cases, the additives may be added at one or more locations for most effectiveness.
At these various locations, the instant inhibitor additive system can also be added with a carrier or additive typically used in paper making, such as retention aids, sizing aids and solutions, starches, precipitated calcium carbonate, ground calcium carbonate, or other clays or fillers, and brightening additives.
The following examples are for illustrative purposes only and are not to be construed to limit the instant invention in any manner whatsoever.
Handsheet Treatment
All additives are applied by syringe-injecting the appropriate weight % of additive combination in either an aqueous solution when the additive is water soluble, or a solution in 1:1 (ethanol/dioxane) onto bleached thermomechanical pulp (BTMP) brightness squares (4 cmxc3x974 cm). The clamped sheets are allowed to air dry for one day.
The brightness of the handsheets is recorded before and after treatment by light exposure.
Accelerated testing is carried out by subjecting the treated sheets to accelerated light induced yellowing in a fan-cooled light box containing eight fluorescent lamps with a spectral maximum output at 5700 xc3x85 with a total output approximately 43 times greater than normal office fluorescent lamps. The lamps are only about ten inches away from the handsheets being illuminated.
Ambient testing is carried out by placing the treated handsheets on a desk under normal cool-white fluorescent office lights at a nominal distance of six feet.
In both case ISO brightness is tracked as a function of photolysis time and converted to post color number (PC number) in the usual manner. (Giertz, Svensk Papperstidn, (1945) 48 (13), 317)
Post color (PC) number is defined as follows:
PC=[(k/s)afterxe2x88x92(k/s)before]xc3x97100
k/s=(1xe2x88x92Rinf)2/2Rinf 
where k and s are the absorption and scattering coefficients, respectively, and Rinf is the value of ISO brightness.
The relationship between Rinf and the chromophore concentration is non-linear, whereas, the PC number is roughly linearly related to the concentration of the chromophore in the sample.
Low PC numbers are desired as they indicate less yellowing.
When using the ambient test conditions untreated BTMP handsheets are compared to Kraft handsheets, after 60 days the BTMP handsheets have a PC number which is about 10 while the Kraft paper has a PC number which is 0.388742. The Kraft handsheets are clearly less yellow than untreated BTMP handsheets after exposure to ambient light.
The incident light flux for the accelerated yellowing experiments (Examples 1-4) is 43 times greater than normal office fluorescent lamps as measured by the A. W. Speery SLM-110 digital light power meter. The brightness of the handsheets is tracked and compared to that of untreated sheets exposed in the same manner. The treated sheets exhibit significant resistance to yellowing as seen below.
Materials Used in the Examples
Compound A is 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidine;
Compound B is 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine;
Compound C is 1-oxyl-2,2,6,6-tetramethyl-4-acetamidopiperidine;
Compound D is 1-oxyl-2,2,6,6-tetramethylpiperidine TEMPO;
Compound E is bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)sebacate;
Compound F is 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium chloride;
Compound G is 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium bisulfate;
Compound H is bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)sulfate;
Compound I is 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium acetate;
Compound J is pentakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)diethylenetriaminepentaacetic acid;
Compound K is 3-(4-benzyloxy-2,2,6,6-tetramethyl-piperidin-1-yloxy)-propionic acid methyl ester;
Compound L is 3-(4-{4-[1-(2-methoxycarbonyl-ethoxy)-2,2,6,6-tetramethyl-piperidin-4-yloxymethyl]-benzyloxy}-2,2,6,6-tetramethyl-piperidin-1-yloxy)-propionic acid methyl ester;
Compound M is 2,2-diethyl-malonic acid bis-(1-butylcarbamoyloxy-2,2,6,6-tetramethyl-piperidin-4-yl) ester;
Compound N is acetic acid 4-hydroxy-2,2,6,6-tetramethyl-piperidin-1-yl ester;
Compound O is benzoic acid 1-butoxycarbonyloxy-2,2,6,6-tetramethyl-piperidin-4-yl ester;
Compound P is 2,2,6,6-tetramethyl-1-(1-phenyl-ethoxy)-piperidin-4-ol;
Compound Q is 2,4-dihydroxybenzophenone;
Compound R is 12-hydroxy-3,6,9-trioxadodecyl-3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamate (Tinuvin(copyright) 1130);
Compound S is, 3-(2H-benzotriazol-2-yl)-4-hydroxy-5-(1-methylpropyl)-benzenesulfonic acid monosodium salt (Cibafast(copyright) W);
Compound T is 1-oxyl-2,2,6,6-tetramethyl-4-(2,3-dihydroxypropoxy)piperidine;
Compound U is 1-oxyl-2,2,6,6-tetramethyl-4-(carboxymethoxy)piperidine;
Compound V is 3-oxyl-1,2,2,4,4-pentamethyl-3,4-dihydro-2.H.-imidazol-1-ium methylsulfate;
Compound W is 3-(3-benzotriazol-2-yl-5-.tert.-butyl-4-hydroxy-phenyl)-propionic acid;
Compound X is polyethylene glycol of molecular weight 300 (PEO);
Compound Y is 4,6-bis(2,4-dimethylphenyl)-2-(4-(3-dodecyloxy*-2-hydroxypropoxy)-2-hydroxyphenyl)-s-triazine (*is mixture of C12-14oxy isomers) (Tinuvin(copyright) 400);
Compound Z is 2,2xe2x80x2-dihydroxy-4,4xe2x80x2-dimethoxy-5,5xe2x80x2-disulfobenzophenone, disodium salt (Uvinul(copyright) 3048);
Compound AA is 2,2xe2x80x2-dihydroxy-4,4xe2x80x2-dimethoxybenzophenone (Uvinul(copyright) 3049);
Compound BB is diethylenetriamine tetraacidic acid (DTPA);
Compound CC is 5,5-dimethyl-1-pyrroline N-oxide;
Compound DD is N-tert-butyl-xcex1-phenylnitrone;
Compound EE is 1-oxyl-2,2,6,6-tetramethyl-4-oxo-piperidine;
Compound FF is tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)citrate;
Compound GG is dithiothreitol;
Compound HH is 1-thioglycerol;
Compound II is 2,2xe2x80x2-oxydiethanethiol;
Compound JJ is 2,2,6,6-tetramethyl-4-acetamidopiperidine;
Compound KK is UVINUL(copyright) 3000, 2,4-dihydroxybenzophenone;
Compound LL is Brightener 28; 4,4xe2x80x2-bis[4-anilino-6-(bis(2-hydroxyethyl)amino-s-triazin-2-yl]amino-2,2xe2x80x2-stilbenedisulfonic acid, disodium salt;
TMHP is 2,2,6,6-tetramethyl-4-hydroxypiperidine.